1. Field of the Invention
The present invention relates to data transmission, and more particularly, it relates to a method for passing data from an external memory device through a buffer to a data processor.
2. Description of the Related Art
When a data processor retrieves specific data from an external memory device such as an optical disk drive, the specific data is passed from the optical disk through a buffer to the data processor. In this case, the buffer that is x bytes in size usually holds the last x bytes of data that moved between the external memory device and the data processor. Hence, whenever the data processor retrieves new data from the external memory device, the new data replaces the old data stored in the buffer during the previous data retrieval.
Meanwhile, the data structure of an external memory such as a magnetic optical disk includes disk data for identification, directory data and file data. Referring to FIG. 3, the disk data PVD includes identification information relating to the disk, and is the first set of data passed to the data processor whenever file data is retrieved from the disk. The directory data concerns the names, sizes, etc. of the files, having substructure. For example, the uppermost root directory Dr includes subdirectory data Dsa, Dsb, Dsc . . . since each has further substructure. The lowermost subdirectories include corresponding file data F1, F2, F3 . . ., etc. which are passed along with the corresponding subdirectory data. The root directory data Dr is treated along with the disk data PVD.
The general process of passing file data of a storage medium such as a disk to a data processor, includes first retrieving the disk data and passing it through the buffer to the data processor. Second, the directory data identifying the location of the file is retrieved and passed through the buffer to the data processor. Finally, the file data is retrieved and passed through the buffer to the data processor. Thus, the retrieval operation which causes the data pickup to retrieve data from the disk must be repeatedly performed in accordance with the number of data to be accessed.
For example, when a number of file data F1 to F6 are sequentially requested by the data processor, the retrieval data flow is ordered as follows: Dsa.fwdarw.F1.fwdarw.Dsa.fwdarw.F2.fwdarw.Dsa.fwdarw.F3.fwdarw.Dsb.fwdarw. Dsc.fwdarw.F4.fwdarw.Dsc.fwdarw.F5.fwdarw.Dsb.fwdarw.Dsd.fwdarw.F6 following a prior PVD.fwdarw.Dr. operation. Thus, the retrieval data flow includes a repetition of same data (e.g., Dsa, Dsb, Dsc, etc.) to be passed through the buffer during the processing sequence. This decreases the data processing speed.